Loss Of Group Research Articles

Potential Strong Inhibition on Ozone Production Sensitivity by Particle Uptake

The accurate identification of ozone (O3) production sensitivity is central to developing O3 pollution control policies. It is determined by the relative ratio of the radical loss to the total primary radical production. However, such radical losses in the traditional sensitivity analysis typically rely on nitrogen oxide (NOx) sinks while ignoring particle uptake (collisions between compounds in the gas phase and condensed phases that result in irreversible uptake due to chemical reactions). Therefore, we combine NOx and particle uptakes to optimize peroxy radical loss estimates and thus analyze the relative sensitivity. We also assess the absolute responses of precursor reduction to O3 production. Such relative and absolute sensitivity analysis is applied to measurements in Chun’an, a county in China, where volatile organic compounds (VOCs) and NOx are both rich. Consequently, the relative sensitivity analysis presents that the dominant precursor for O3 production sensitivity shifts from volatile organic compounds (VOCs) in the morning and evening to NOx in the afternoon, the main driver of which is related to NO depletion. In contrast, the absolute sensitivity analysis confirms that VOCs persistently determine the diurnal ozone production sensitivity. Moreover, they both show that particle uptake does not change the regime classification of O3 production sensitivity (i.e., VOC- or NOx-sensitive regime) but potentially has a strong inhibition on the sensitivity magnitude (within 16% and 38% for VOC- or NOx-sensitive regimes, respectively). Our results partly explain more insensitive O3 production measurements than those suggested by traditional sensitivity analyses, which has important implications for synergistic controls on O3 and fine particulate matter pollution.

Potential Factors Contributing to Ozone Production in AQUAS-Kyoto Campaign in Summer 2020: Natural Source-Related Missing OH Reactivity and Heterogeneous HO2/RO2 Loss.

This study presents total OH reactivity, ancillary trace species, HO2 reactivity, and complex isoprene-derived RO2 reactivity due to ambient aerosols measured during the air quality study (AQUAS)-Kyoto campaign in September, 2020. Observations were conducted during the coronavirus disease (COVID-19) pandemic (associated with reduced anthropogenic emissions). The spatial distribution of missing OH reactivity highlights that the origin of volatile organic compounds (VOCs) may be from natural-emission areas. For the first time, the real-time loss rates of HO2 and RO2 onto ambient aerosols were measured continuously and alternately. Ozone production sensitivity was investigated considering unknown trace species and heterogeneous loss effects of XO2 (≡HO2 + RO2) radicals. Missing OH reactivity enhanced the ozone production potential by a factor of 2.5 on average. Heterogeneous loss of radicals could markedly suppress ozone production under low NO/NOx conditions with slow gas-phase reactions of radicals and change the ozone regime from VOC- to NOx-sensitive conditions. This study quantifies the relationship of missing OH reactivity and aerosol uptake of radicals with ozone production in Kyoto, a low-emission suburban area. The result has implications for future NOx-reduction policies. Further studies may benefit from the combination of chemical transport models and inverse modeling over a wide spatiotemporal range.

Mechanism of nonequilibrium plasma-enhanced ignition in the event of dual-pulse laser energy deposition

A two-dimensional (2D) and three-temperature mathematical model for dual-pulse laser (DPL) ignition was applied to study the mechanism of the nonequilibrium plasma (NEQP) process during DPL energy deposition. The 2D model could predict the influence of the reaction kinetics and nonequilibrium effects on the ignition delay time and kernel dynamics. As the plasma reaction rates were extremely fast compared with the combustion reaction rates, it can be predicted that the variability of the plasma lifetime will directly influence the ignition delay time and reaction kinetics. The results suggested that the energy relaxation rate from the electronic state was rapid compared to that from the vibrational state due to the short lifetime of the plasma state. However, the relatively slower energy relaxation from the vibrational state provided long-term thermalization of the ignition kernel. For the same level of energy deposition, the NEQP system predicted a higher rate of vorticity generation, signifying a higher level of mixing and baroclinicity production. The results also suggested that ignition in a premixed fuel airflow required a higher degree of energy deposition, due to a higher rate of radical and thermal losses.

Volatile organic compounds in urban Lhasa: variations, sources, and potential risks

Lhasa is a typical high-altitude city with strong solar radiation and high background ozone levels. With the rapid development and urbanization, the emission of volatile organic compounds (VOCs) in Tibet has been increasing annually. However, VOCs activity and the impact on air quality and human health have scarcely been investigated. We conducted online measurement of VOCs in urban Lhasa during May 2019. The mean mixing ratio (with one standard deviation) of the total VOCs was 21.5 ± 18.6 ppb. Of the total VOCs, alkanes, alkenes, and aromatic hydrocarbons accounted for 57.7%, 20.9%, and 21.4%, respectively. On the basis of VOC atmospheric reactivity, the ozone formation potential (OFP) and hydroxyl radical loss rate (LOH) were 91.7 ppb and 3.1 s−1, respectively. Alkenes accounted for the largest proportion of the OFP and LOH, followed by aromatic hydrocarbons. The results of correlation analysis on the benzene series (BTEX), and the similarity of the diurnal changes in CO, NOy, BTEX, and TVOC mixing ratios indicated that Lhasa city strongly affected by motor vehicle emissions. Source apportionments using positive matrix factorization (PMF) model further confirmed that traffic related emissions, including gasoline automobiles, diesel vehicles, and public transportation vehicles fueled with liquid natural gas contributed the most in total VOCs concentration (44.5%–50.2%), LOH (41.6%–46.8%) and OFP (47.4%–52.3%). Biomass combustion, mainly from the traditional biomass fuel in the plateau, was the second contributor to ambient VOCs (41.3%), LOH (26.4%), and OFP (29.7%), and existed a less variation in diurnal changes with a feature of regional background. Plants contributed only about 1.5% to the VOCs concentration but a relatively high (approximately 14.6%) LOH. The noncarcinogenic risk of BTEX did not exceed the hazard quotient value, but the carcinogenic risk of benzene was 4.47 × 10–6, indicating a potential risk.

UV absorption spectrum of monochlorodimethyl sulfide (CH3SCH2Cl)

Monochlorodimethyl sulfide (CH3SCH2Cl, MCDMS) is a trace gas thought to be formed in the marine environment via the reaction of Cl2 with dimethyl sulfide (DMS, CH3SCH3) with implications for the temporal and spatial production of SO2 and sulfate aerosol formation. In this study, the room temperature UV absorption spectrum of MCDMS in the 200–330 nm wavelength region was measured. The spectrum measured in this work differs significantly in the long-wavelength actinic region, >295 nm, from that reported previously by Copeland et al. (Environ. Sci. Technol., 2014, 48, 1557–1565). On the basis of the present results, the MCDMS first-order tropospheric photolysis rate coefficient is a factor of ∼250 less than reported in Copeland et al. The diurnally averaged MCDMS photolysis lifetime is estimated to be ∼125 days at ground level for Summer mid-latitude conditions over the ocean. UV photolysis is, most likely, a minor gas-phase degradation pathway for MCDMS compared to its OH radical and Cl-atom reactive losses.

Characteristics and Reactivity of VOCs in a Typical Industrial City in Summer

To investigate the ambient pollution caused by volatile organic compounds (VOCs) in a typical industrial city in summer, the characteristics and chemical reactivity from VOCs and the causes of ozone (O3) pollution were analyzed using online VOCs measurements during polluted and non-polluted periods in Zibo city in July 2020. The results showed that the average hourly concentration of total volatile organic compounds (TVOC) during the polluted period[(50.6±28.3)] μg·m-3 was 32.5% higher than that during the non-polluted period[(38.2±24.9) μg·m-3]. The contribution of all VOCs categories were as follows:alkanes>aromatics>alkenes>alkynes, and the diurnal averages of TVOC and O3 concentrations were opposite during the polluted and non-polluted period. Ozone formation potential (OFP),·OH radical loss rate (L·OH), and secondary organic aerosol formation potential (SOAp) during the polluted period were higher than those during the non-polluted period. Alkenes contributed most to OFP and L·OH, whereas aromatics contributed most to SOAp. The tendency of the diurnal average of OFP and SOAp was overall consistent with that of TVOC. The priority species of OFP, L·OH, and SOAp were alkenes and aromatics. The VOCs/NOx method was applied to identify the O3-VOC-NOx sensitivity during the polluted and non-polluted periods, and the results showed that the photochemical regimes were VOCs-limited and transition regions. In addition, the smog production model (SPM) was employed to identify the O3 formation regime, and the results showed that those during the polluted period were identified as VOCs-limited and transition regions from 08:00 to 16:00, whereas the non-polluted period was mainly considered to be VOCs-limited. To mitigate the O3 pollution in summertime, the synergistic control of VOCs (especially alkenes and aromatics) and NOx emissions should be enforced.

Characteristics and Sources of Volatile Organic Compounds in the Nanjing Industrial Area

In this study, 56 volatile organic compounds species (VOCs) and other pollutants (NO, NO2, SO2, O3, CO and PM2.5) were measured in the northern suburbs of Nanjing from September 2014 to August 2015. The total volatile organic compound (TVOC) concentrations were higher in the autumn (40.6 ± 23.8 ppbv) and winter (41.1 ± 21.7 ppbv) and alkanes were the most abundant species among the VOCs (18.4 ± 10.0 ppbv). According to the positive matrix factorization (PMF) model, the VOCs were found to be from seven sources in the northern suburbs of Nanjing, including liquefied petroleum gas (LPG) sources, gasoline vehicle emissions, iron and steel industry sources, industrial refining coke sources, solvent sources and petrochemical industry sources. One of the sources was influenced by seasonal variations: it was a diesel vehicle emission source in the spring, while it was a coal combustion source in the winter. According to the conditional probability function (CPF) method, it was found that the main contribution areas of each source were located in the easterly direction (mainly residential areas, industrial areas, major traffic routes, etc.). There were also seasonal differences in concentration, ozone formation potential (OFP), OH radical loss rate (LOH) and secondary organic aerosols potential (SOAP) for each source due to the high volatility of the summer and autumn temperatures, while combustion increases in the winter. Finally, the time series of O3 and OFP was compared to that PM2.5 and SOAP and then they were combined with the wind rose figure. It was found that O3 corresponded poorly to the OFP, while PM2.5 corresponded well to the SOAP. The reason for this was that the O3 generation was influenced by several factors (NOx concentration, solar radiation and non-local transport), among which the influence of non-local transport could not be ignored.

Whistleblowing and the press: Complicating the standard account

Whistleblowers and journalists are key democratic actors who are both concerned with the exposure of wrongdoing in corporations, organizations, and governments. For that reason, they often collaborate to bring incriminating information to public knowledge. In the standard account, the whistleblower initiates the contact to journalists who eventually publish the story. Based on a sample of 16 whistleblower cases, the paper shows that the reality of this relationship is more complex than the standard account suggests. The empirical material documents four different trajectories through which whistleblower information reaches the public sphere, only one of which conforms to the standard account. The paper explains the variation based on a theoretical framework, which highlights the main similarities and differences between whistleblowers and journalists. Seen from the perspective of whistleblowers the relationship is double-sided. On the one hand, engaging with the press entails considerable asymmetry and uncertainty for whistleblowers who do not always know the exact motives of journalists just as they enter the relationship from a much more precarious and unstable position. Whistleblowers are also wary of collaborating with the press because it entails a radical loss of privacy as the story breaks in the public sphere. On the other hand, interacting with the press can offer vital legitimacy, protection, and professional resources for vulnerable whistleblowers. Existing work on this core relationship in democracy is surprisingly small and undertheorized. The paper contributes to the debate by offering a theoretically and empirically grounded typology of the whistleblower-journalism nexus.

Spatiotemporal variation, source and secondary transformation potential of volatile organic compounds (VOCs) during the winter days in Shanghai, China

The spatiotemporal concentration variations, sources, and secondary transformation potential of volatile organic compounds (VOCs) were analyzed at three sampling sites, including the rural (DSL), urban (PD) and industrial (JS) sites, in December 2019, in Shanghai, China. The VOC concentrations in the DSL, PD and JS sites were 13.32 ± 3.33 ppb, 24.72 ± 4.31 ppb and 30.66 ± 5.83 ppb, respectively. The observed “weekend effects” showed the importance of traffic levels and human activities at weekend. By the PMF model, vehicle emission was identified as the largest source of VOCs, accounting for 34.29% in the DSL site, 35.38% in the PD site and 30.07% in the JS site, respectively. During the observation period, in addition to the local sources, regional transport from the provinces nearby was an essential source for VOCs. Although alkanes were the most abundant VOC species in Shanghai, alkenes were the species with the highest chemical activity according to the measurements of OH radical loss rate (LOH) and ozone formation potential (OFP), which played the dominant roles in ozone formation. Haze pollution was largely driven by secondary aerosol formation. The SOA yields from VOCs were 11.29 ± 7.21 μg/m3 and 18.91 ± 8.36 μg/m3 in the clean and haze days, respectively, with aromatics, especially toluene, being the most abundant precursor. The SOA yields in the JS site were much higher than those at the other two sites during the measurement. The VOCs in the DSL site held the highest sensitivity to PM2.5, followed by the JS and PD sites, and aromatics were more sensitive to PM2.5 than other VOC species. Thus, the critical way to reduce PM2.5 formation in Shanghai, especially in the industrial sites, is controlling the concentration of aromatics. This study highlights the vehicle-related source and the secondary transformation from VOCs, which can provide references for local governments regarding controlling strategies of VOCs.

Lessons from COVID-19 for GCR governance: a research agenda

The Lessons from Covid-19 Research Agenda offers a structure to study the COVID-19 pandemic and the pandemic response from a Global Catastrophic Risk (GCR) perspective. The agenda sets out the aims of our study, which is to investigate the key decisions and actions (or failures to decide or to act) that significantly altered the course of the pandemic, with the aim of improving disaster preparedness and response in the future. It also asks how we can transfer these lessons to other areas of (potential) global catastrophic risk management such as extreme climate change, radical loss of biodiversity and the governance of extreme risks posed by new technologies. Our study aims to identify key moments- ‘inflection points’- that significantly shaped the catastrophic trajectory of COVID-19. To that end this Research Agenda has identified four broad clusters where such inflection points are likely to exist: pandemic preparedness, early action, vaccines and non-pharmaceutical interventions. The aim is to drill down into each of these clusters to ascertain whether and how the course of the pandemic might have gone differently, both at the national and the global level, using counterfactual analysis. Four aspects are used to assess candidate inflection points within each cluster: 1. the information available at the time; 2. the decision-making processes used; 3. the capacity and ability to implement different courses of action, and 4. the communication of information and decisions to different publics. The Research Agenda identifies crucial questions in each cluster for all four aspects that should enable the identification of the key lessons from COVID-19 and the pandemic response.

Effects of C5a and Receptor CD88 on Glutamate and N-Methyl-D-Aspartic Acid Receptor Expression in the Mouse Model of Optic Neuromyelitis

Objective To analyze the role of C5a, C5a receptor (CD88), glutamic acid, and N-methyl-D-aspartic acid receptors (NMDAR1 and NMDAR2B) in the onset of neuromyelitis optica (NMO) disease in mice. Method To select C57BL/6 wild-type (WT) mice and C5a receptor gene knockout (C5aR-/-) mice, use NMO-IgG and hemolytic complement to intervene in spinal cord tissue sections and optic nerves to establish an NMO model in vitro. The experiment was carried out with five groups (control group, WT group, C5aR-/- group, C5a group, and C5a+C5aRA group), with six mice in each group. The differences of American spinal cord injury (ASIA) motor scores were compared among all groups. The expressions of aquaporin (AQP4), glial fibrillary acidic protein (GFAP), NMDAR1, and NMDAR2B in spinal cord and optic nerve tissues were detected. The difference of glutamic acid (Glu) concentrations in culture solutions of the spinal cord and optic nerves was compared. Result The ASIA motor score of the control group was significantly lower than that of the other four groups. The C5a-/- group was significantly higher than the WT group. The C5a+C5aRA group was significantly higher than the C5a group in terms of ASIA motor score. In the control group, AQP4 and GFAP showed expression loss. The C5aR-/- group's loss rate was significantly higher than that of the WT group. The loss rate of the C5a+C5aRA group was significantly higher than that of the C5a group. In the control group, the protein expressions of NMDAR1 and NMDAR2B were significantly lower than that of the other four groups. The C5aR-/- group was significantly higher than the WT group. The C5a+C5aRA group was significantly higher than the C5a group in protein expression. In the control group, the concentration of Glu in the C5aR-/- group was significantly higher than that in the WT group, and the C5a group was significantly lower than the C5a+C5aRA group. Conclusion The deletion of the C5a receptor promotes NMDAR activity, which affects the toxic excitatory effect of NMDAR in NMO and regulates the neurotoxic effect of glutamic acid, thus participating in the pathogenesis of NMO.

A Microhistory of Anna Frajlich's Émigré Experience

Abstract This article is an anthropological and literary analysis of the letters written by Anna Frajlich, her husband, and sister to Frajlich's parents, Amalia and Psachie Frajlich. The correspondence begins the moment they left Poland in November 1969, forced into exile as a result of the government-sponsored anti-Semitic campaign, political and social repression, and merciless propaganda directed against citizens of Jewish nationality. The correspondence ends with Frajlich's parents’ arrival in the United States in June 1971. The letters are examined as a microhistory marked with a female signature, in which it is important to expose the subjective awareness of the determination of an individual's fate by an external situation, to see the complex process, complications and consequences of throwing the individual and her loved ones into the whirlwind of history. The correspondence shows the experience of being deprived of the possibility to be “at home,” documents this radical loss, and gives it a personal dimension. It emphasizes the importance of family, her intimate world, and the individual focused on the issue of redefining her identity. The parameters of that dimension are set by those close to them, their intimate world, individuals living in the here and now, oriented toward self-understanding. The horizon of expectations and the will to knowledge are determined by the most important element in an authentic encounter with the self—the desire to protect oneself and those around her from chaos and uncertainty.

Multispecies mourning: grieving as resistance on the West Papuan plantation frontier

ABSTRACT This article explores the cultural, political, and affective significance of mourning among the Indigenous Marind communities of rural Merauke West Papua, whose intimate and ancestral relations to native plants, animals, and ecosystems are increasingly threatened by mass deforestation and monocrop oil palm expansion. Cross-pollinating Indigenous more-than-human philosophies with environmental humanities scholarship, I examine three emergent practices of ‘multispecies mourning’ on the Papuan oil palm frontier – the weaving of sago bags as a form of collective healing, the creation of songs prompted by encounters with roadkill, and the transplanting of bamboo shoots as part of customary land reclaiming activities. Multispecies mourning offers potent avenues for Marind to memorialize the radical loss of lives and relations prompted by capitalist landscape transformations. At the same time, multispecies mournings constitute forms of active resistance and creative refusal in the face of extractive capitalism’s ecocidal logic. Bringing together plants, people, and places, their dispersed sentience and materiality offer hopeful pathways for multispecies solidarities, in and against the rubble of agro-industrialism and its necropolitical undergirdings.

Characteristics, source analysis and chemical reactivity of ambient VOCs in a heavily polluted city of central China

From 2020.8.21 to 2020.9.30, continuously atmospheric volatile organic compounds (VOCs) were measured in the Central Plain to analyze the pollution characteristic, source distribution, chemical reactivity, and contribution to the formation of O3. The concentration of total VOCs (TVOC) was 29.47 ± 13.78 ppbv, and the main VOCs component was alkanes (46%). Ethane, propane, and n-butane were the first three species of VOCs. Six emission sources were identified through positive matrix decomposition (PMF) model, including biogenic source (4%), vehicle emission (28%), fuel evaporation (7%), industrial source (27%), solvent usage (23%) and combustion (11%). Backward trajectory analysis showed that VOCs were mainly derived from short-distance air masses (51%) traveling southeast of Zhengzhou, with the average mixing ratio of VOCs was 31.87 ppbv. Through the potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) models, Zhengzhou and its surrounding areas are the main potential sources areas of VOCs. Finally, results of the OH radical loss rate (LOH) and ozone formation potential (OFP) showed that alkenes and aromatics were the species with highest chemical activity, of which both LOH was 34%, and aromatics contributes the most to the formation of O3, accounting for 49%. In addition, solvent usage, industrial source, and vehicular emission were important sources to OFP.

Spatial characteristics of VOCs and their ozone and secondary organic aerosol formation potentials in autumn and winter in the Guanzhong Plain, China

As critical precursors of tropospheric ozone (O3) and secondary organic aerosol (SOA), volatile organic compounds (VOCs) largely influence air quality in urban environments. In this study, measurements of 102 VOCs at all five major cities in the Guanzhong Plain (GZP) were conducted during Sep.09-Oct. 13, 2017 (autumn) and Nov. 14, 2017–Jan. 19, 2018 (winter) to investigate the characteristics of VOCs and their roles in O3 and SOA formation. The average concentrations of total VOCs (TVOCs) at Xi'an (XA), Weinan (WN), Xianyang (XY), Tongchuan (TC), and Baoji (BJ) sites were in the range of 55.2–110.2 ppbv in autumn and 42.4–74.3 ppbv in winter. TVOCs concentrations were reduced by 22.4%–43.5% from autumn to winter at XA, WN and BJ. Comparatively low concentrations of TVOCs were observed in XY and TC, ranging from 53.5 to 62.7 ppbv across the sampling period. Alkanes were the major components at all sites, accounting for 26.4%–48.9% of the TVOCs during the sampling campaign, followed by aromatics (4.2%–26.4%). The average concentration of acetylene increased by a factor of up to 4.8 from autumn to winter, indicating the fuel combustion in winter heating period significantly impacted on VOCs composition in the GZP. The OH radical loss rate and maximum incremental reactivity method were employed to determine photochemical reactivities and ozone formation potentials (OFPs) of VOCs, respectively. The VOCs in XA and WN exhibited the highest reactivities in O3 formation, with the OFP of 168–273 ppbv and the OH loss rates of 19.3–40.8 s−1. Alkenes and aromatics primarily related to on-road and industrial emissions contributed 57.8%–76.3% to the total OFP. The contribution of aromatics to the SOA formation at all sites reached 94.1%–98.6%. Considering the potential source-area of VOCs, regional transport of VOCs occurred within the GZP cities.

Comparison of VOCs Pollution Characteristics Between an Urban Site and a Background Site in Summer in Zibo

To study the differences in volatile organic compound (VOCs) pollution characteristics between an urban site and a background site in summer, ambient VOCs were monitored using an online gas chromatograph (GC) at an urban site and a background site (Mt. Lu) in Zibo in July 2020. The VOCs pollution characteristics and chemical reactivity were analyzed, and the sources of VOCs were identified using the positive matrix factorization model(PMF). The results showed that ρ(TVOC) and ρ(NOx) were higher at the urban site, but ρ(O3) was higher at the background site. Diurnal average characteristics of ρ(TVOC) and ρ(NOx) were high at night and low during the day at the urban site, and there were no obvious variation characteristics at the background site. The diurnal average characteristics of ρ(O3) were consistent at the urban and background sites, showing low level at night and high level during the day; however, the peak in the background site was later than that at the urban site. The average ρ(TVOC) at the urban site and background site were (44.9±27.5) μg·m-3 and (17.3±9.1) μg·m-3, respectively, and the mass fraction of each component was ordered as alkanes>aromatics>alkenes>alkynes in both sites. The average ozone formation potentials(OFP)were (115.5±63.1) μg·m-3 and (38.0±20.2) μg·m-3, and the contribution of each component was ordered as alkenes>aromatics>alkanes>alkynes. The respective average values of·OH radical loss rate(L·OH) were (3.9±2.3) s-1 and (1.0±0.6) s-1, with the highest contribution of alkenes and the lowest contribution of alkynes in both sites. The average values of secondary organic aerosol formation potential(SOAp) were (0.5±0.3) μg·m-3 and (0.2±0.06) μg·m-3, respectively, with aromatic being the most abundant group. According to the source appointment by the PMF model, the main source of VOCs in the urban site was traffic sources (52.4%), followed by petroleum evaporation (19.2%), solvent evaporation (17.3%), and oil and biological sources (11.1%). The source of VOCs in the background site mainly came from traffic sources (40.2%), followed by solvent evaporation (31.3%), combustion sources (19.3%), and biological sources (9.2%). Zibo City should strengthen the management and control of motor vehicle emissions, petroleum evaporation, and the use of industrial solvents.

Investigation of VOC characteristics, source analysis, and chemical conversions in a typical petrochemical area through 1-year monitoring and emission inventory.

To effectively investigate the characteristics, source analysis, and chemical conversions of volatile organic compounds (VOCs) pollution in a typical petrochemical area, 81 VOC species from nine sampling sites were collected from 1st January to 31th December 2019 in Jinshan District. Results showed the concentration of VOCs was 51.63 ± 36.05 ppbv, and VOCs were dominated by alkane (40.10%) and alkenes (39.91%). The temporal variations of VOCs showed that the highest average VOC concentration appeared in July, and the lowest concentration of VOCs was in February. The concentration of VOCs was mainly connected with industrial processes and was transported to other areas through the downwind direction. Six PMF-derived sources including petrochemical industry, solvent utilization, vehicle exhaust, fuel evaporation, combustion, and other industry processes, contributing 37.08%, 16.74%, 16.69%, 14.99%, 9.53%, and 4.97%, respectively. Meanwhile, an anthropogenic VOC emission inventory was established by emission factors and the activity statistics for 2019, results indicated that the total emission of VOCs was estimated as 6.22 kt, petrochemical industry was the most important contributor of human-produced VOCs. The LOH concentration was 396.12 ppbv via OH radical loss rate method, and the OFP was 210.44 ppbv based on the MIR factor. Alkenes and aromatics were the important components of O3 formation. This study provides effective information for corresponding governments to establish VOCs contamination control directives.

Mass spectrometry based fragmentation patterns of nitrosamine compounds.

Nitrosamines are a class of mutagenic substances that can display high carcinogenic potential. New chemical entities may have the potential to form unique nitrosamines specific to the drug substance. It is therefore essential to understand the gas-phase fragmentation behavior of nitrosamine compounds to enable the development of analytical methods to characterize novel nitrosamine compounds. The gas-phase fragmentation behavior of eight model nitrosamine compounds representing the common substructures seen in many small molecule pharmaceutical compounds was studied with positive electrospray ionization tandem mass spectrometry (ESI-MS/MS). The fragmentation patterns of these compounds under various collision parameters available in commercially available mass spectrometers were studied. Protonated nitrosamine compounds produced diagnostic fragment ions upon MS/MS. Three primary structure-dependent fragmentation pathways were observed. The first pathway involves the loss of 30 Da which corresponds to the loss of the NO radical from the protonated nitrosamine compound (Group 1). The second and third fragmentation pathways, which have not been reported for nitrosamine compounds, proceed via the loss of H2 O from the protonated nitrosamine compound (Group 2), and elimination and a loss of 46 Da (loss of NH2 NO) from the nitrosamine compound (Group 3). Results presented in this work provide an overview of the gas-phase fragmentation patterns of nitrosamine compounds and may be useful in identifying novel nitrosamine compounds in complex matrices.

Localization of Intrachain Modifications in Bacterial Lipids Via Radical-Directed Dissociation.

Intrachain modifications of membrane glycerophospholipids (GPLs) due to formation of the carbon-carbon double bond (C═C), cyclopropane ring, and methyl branching are crucial for bacterial membrane homeostasis. Conventional collision-induced dissociation (CID) of even-electron ions of GPL favors charge-directed fragmentation channels, and thus little structurally informative fragments can be detected for locating intrachain modifications. In this study, we report a radical-directed dissociation (RDD) approach for characterization of the intrachain modifications within phosphoethanolamines (PEs), a major lipid component in bacterial membrane. In this method, a radical precursor that can produce benzyl or pyridine methyl radical upon low-energy CID at high efficiency is conjugated onto the amine group of PEs. The carbon-centered radical ions subsequently initiate RDD along the fatty acyl chain, producing fragment patterns key to the assignment and localization of intrachain modifications including C═C, cyclopropane rings, and methyl branching. Besides intrachain fragmentation, RDD on the glycerol backbone produces fatty acyl loss as radicals, allowing one to identify the fatty acyl chain composition of PE. Moreover, RDD of lyso-PEs produces radical losses for distinguishing the sn-isomers. The above RDD approach has been incorporated onto a liquid chromatography-mass spectrometry workflow and applied for the analysis of lipid extracts from Escherichia coli and Bacillus subtilis.

Low-molecular-weight carbonyl volatile organic compounds on the North China Plain

To understand the photochemical pollution characteristics of low-molecular-weight carbonyl compounds on the North China Plain (NCP), 2,4-dinitrophenylhydrazine (DNPH) was used to sample low-molecular-weight carbonyl compounds in the atmosphere in Beijing, Tianjin, Shijiazhuang, Xianghe and Xinglong from June 2019 to January 2020, and the samples were then analyzed by a high-performance liquid chromatography (HPLC) to obtain the concentration, daytime variations, seasonal variations, OH radical loss rate, ozone formation potential and sources of five low-molecular-weight carbonyl compounds in the NCP region. The total concentrations at the five sites were 7.70 ± 1.94 ppbv (Beijing), 10.20 ± 1.83 ppbv (Tianjin), 15.31 ± 2.35 ppbv (Shijiazhuang), 10.53 ± 1.82 ppbv (Xianghe) and 5.42 ± 1.15 ppbv (Xinglong), respectively. The contribution of primary source from anthropogenic emission was higher in Tianjin, Shijiazhuang and Xianghe than that in Beijing. The primary and secondary generation contributions were similar in Xinglong. The concentration in Beijing was highest in autumn and lowest in winter. For Tianjin, Shijiazhuang, Xianghe and Xinglong, the highest concentrations occurred in summer. At the five sites, formaldehyde and acetaldehyde contributed the most to L·OH and OFP, while acetone contributed the least. Both L·OH and OFP in Shijiazhuang were the highest, and those in Xinglong were the lowest. The North China Plain was mainly influenced by short-range airflow from the sea and coastal areas during the summer, with the airflow mainly coming from the south in autumn, while the long-range air mass transport was more influential during the winter. In addition, most pollutants were found to be generated locally. By utilizing a source-tracer-ratio method in the source analysis, with the change of season, the anthropogenic source contribution of each site was found to gradually increase while that of other sources gradually decreased.